“The Sanders campaign’s false attacks have gotten out of hand,” Clinton’s campaign manager Robby Mook said in a statement. “It is shameful that Senator Sanders has resorted to irresponsible and misleading attacks just to raise money for himself.”

In a letter sent to the Democratic National Committee, Sanders argued that the joint fundraising by the DNC and Clinton’s presidential campaign raises “serious apparent violations” of the campaign finance laws, and that they should “cease immediately.”

The Sanders campaign argued that the Clinton campaign violated legal limits on campaign donations by paying members of Clinton’s campaign staff with money from the joint DNC-Clinton committee.

Mook said Sanders should stay focused instead on the issues.

“Instead of trying to convince the next generation of progressives that the Democratic Party is corrupt, Senator Sanders should stick to the issues and think about what he can do to help the Party he is seeking to lead,” Mook said in the statement.

Mook also said that the Vermont senator should drop his lawsuit against the DNC.

“Furthermore, we call on Senator Sanders to end his frivolous and cynical lawsuit against the DNC, which continues to drain resources needed to help Democrats up and down the ticket win in November,” Mook said, “and protect the progress we’ve made under President Obama.”

The back-and-forth comes one day before the New York primary, and as the battle between Clinton and Sanders turns increasingly contentious.